Live Specimens in the S.E.M.

Developing a Technique for Observing Live Specimens in the S.E.M.

In 1973 I was working at a semiconductor company doing electronic engineering and while teaching myself to use the scanning electron microscope in off hours, I developed and perfected a technique to observe and image certain living animal and plant specimens alive, in their natural state, without any kind of fixation or conductive coating. This technique uses the natural conductivity of living specimens to conduct away the charge of the electron beam by using lower than “normal” voltages on the scanning beam and tweaking the electronics and electron detection systems for high sensitivity. You won’t find any mention of this in any of the many microscopy reference books because these techniques have never been formally acknowledged by the scientific community, most likely because I have not published a scientific paper on the subject--although well known to the editors of these reference books on scanning electron microscopy. (Just published that paper: Microscopy Today, January 2017)

It is a somewhat difficult technique and requires fast work with the specimens and a vacuum system that can pump down to working pressure very quickly so the electron beam can be turned on and imaging can begin in short order because with many live specimens there is only a short time to work before the vacuum renders them unsuitable. Depending on the specimen, the most delicate can only allow a couple of minutes of observation or imaging time, while the hardiest can last for up to an hour or so. Besides capturing still images of insects and plants, I have also captured insects and mites alive and moving on real-time video with the SEM as early as 1988, which was probably the first time this was ever done.